The present invention relates generally to a reverse flush filter system provided between a mechanical seal and a pump impeller of a pump.
Pumps having mechanical seals, such as centrifugal pumps, are used in a number of applications involving the transfer of fluids. Fluids transferred by pumps often contain abrasive materials, such as sand or clay, or fibrous materials, such as paper pulp. Unfortunately, when fluids containing such abrasive or fibrous materials are transferred by a pump, a seal cavity of the pump becomes increasingly filled with deposits of the abrasive or fibrous materials. Deposits of these materials not only tend to abrade the rotating surfaces, but also tend to clog the moving components of the mechanical seal, thereby degrading the sealing surfaces of the mechanical seal. Further, such abrasive or fibrous material deposits restrict the capacity of the mechanical seal to compensate for radial and axial shaft deflection and face wear. In many instances, premature seal failures occur due to the clogging and degrading effects of abrasive or fibrous material deposits on the seal.
Conventionally, material deposits are flushed from the seal cavity by injecting clean fluid, such as water, into the seal cavity. However, injecting clean fluid into the seal cavity merely dilutes dirty fluid already present in the seal cavity. Eventually, as the concentration of material deposits in the seal cavity increases, paths develop where the clean fluid injected into the seal cavity flows, causing the material deposits to precipitate in the seal area.
When the material deposits precipitate in the seal area in this manner, large quantities of clean fluid must be used to flush the seal cavity. Further, even where large quantities of clean fluid are used to flush the seal cavity, only marginal results are achieved in removing material deposits from the seal cavity. The costs of flushing the seal cavity also increase as the quantity of clean fluid required to flush the seal cavity increases. Further, the costs of flushing the seal cavity must include the cost of removing excess clean fluid from the material being processed by, for example, pumping.